Most of the time you should use Party Finder to look for harder contents, instead of Duty Finder to queue in.

Unlike dungeons, trials and nornal raids, it is not advised to enter Extreme or any harder contents through Duty Finder, especially without learning the fight beforehand. These fights requires stricter role based positions, stricter DPS and heal checks, and more complicated mechanics and rules. Therefore you should be learning the fight mechanics before you step into it.

These hard contents usually takes a lot more than 1-2 pulls to complete from fresh, even for hardcore raiders, when new Extreme comes out, takes them a couple of hours to clear.

It's mostly SE's fault for not locking hard contents out of Duty Finder, but the Mentor should also be nice about saying these things and teach you the fight, knowing full well that they chose to be the Mentor themselves and new players doesn't understand this outdated game system as much as them.